<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <mate name="viewport"
          content="width=device-width,initial-scale=1.maximum-scale=1,minimum-scale=1,user-scalable=no"></mate>
    <title>栅格布局</title>
    <link rel="stylesheet" href="../css/bootstrap.min.css">
    <style>
        * {
            padding: 0px;
            margin: 0px;
        }
        .test {
            width: 300px;
            height: 200px;
            background: #FF0000;
        }
        @media screen and (max-width: 900px) and (min-width: 600px){
            .test {
                width: 100%;
                height: 100px;
                background: #0000FF;
            }
        }

        .test2{
            height: 300px;
            background: #FF0000;
        }
    </style>
</head>
<body>
<div class="sr-only test"></div>
<div class="test2 col-lg-3 col-md-4 col-sm-6 col-xs-12 col-lg-offset-3"></div>
</body>
</html>